How do Mikkel, On Thu, 2007-09-06 at 13:44 -0500, Mikkel L. Ellertson wrote: > Paul Johnson wrote: > > > > I think it is probably better for us non-experts to rely on higher > > level tools than dd when they do this. There is less danger of human > > error. I see many people recommending "partimage" for this job, but it > > appears that is not in Fedora's distribution, and that makes me think > > it is somehow untrustworthy or dangerous. > > > > After copying disks 15 times, testing various methods, I think the > > best approaches I've found are > > > > 1. If two disks are Identical (same brand, same number of sectors, > > cylinders, and all those other things I don't understand very well), > > then the best way to get an exact copy is to run "g4u", which is a > > program that you install on a bootable CDR and its "copydisk" command > > produces an exact byte-for-byte copy of the whole disk, including the > > MBR, partition table, etc. For all I know, it may be using dd under > > the hood, but the "copydisk" command takes the human error out of the > > equation. It gets the boot sector and everything. g4u is about the > > best documented piece of free software I've found. (The best is CVS, > > by far!) > > > > 2. If two disks are not identical, be more cautious. > > > > In the future, here is how I'm going to copy content from 1 disk to > > the other of a different type/size. Boot the system and make sure > > both disks are recognized by the OS. Use gparted to study the > > partition table on the source disk, and then on the target disk, use > > gparted to create partitons that are AT LEAST AS BIG as the originals. > > > > Then copy the content from one to the other. You can use the > > equivalent of dd in gparted--it has a menu driven approach too copy > > one partition to another, and you can apply that one partition at a > > time. You can use dd in a terminal if you want, of course. Using the > > gparted or dd to copy the content is slow because it copies everything > > bit by bit, including the empty parts of the disks. > > > > There are many ways to just copy the files from one system to another. > > These will be faster than dd. Old school Unix people recommend using > > tar or cpio for things like that. For me, this has always worked: > > Mount the 2 partitions, and then run "find /original -xdev | cpio > > -padm /target ". New kids seem to feel comfortable with "cp -Ra". > > Some people recommend avoiding copying the system-created partitions > > like /proc, and /sys when making this copy, but I don't think it is > > really necessary because a re-boot wipes those out anyway and builds > > new ones. > > > > If your target disk is not as big as the source, you should not use dd > > or gparted to copy the content anyway, and so you have to copy the > > content with tar or such. > > > > After you copy the partitions over, then you need to do 2 things > > manually. First, use e2label to check the labels on each partition > > of the first disk and then use e2label to write the same labels on the > > target disk. If you don't do that, chances are the system will not > > boot because Fedora uses labels to find partitions. Note that e2label > > does not work on swap disks, and one must use mkswap with the -L > > option to set a label on a swap partition. Second, run grub to > > re-write the mbr on the target disk. > > > > This has been a humbling experience. If anybody does come with with a > > step by step fool proof way to make this work, I would be really glad > > to hear it. > > > > PJ > Unless you have a good reason for it, dd is not the right tool to > copy a partition from one disk to another. You are much better off > using a tool like parted, or one of the GUI interfaces for it. This > is because parted understands about file systems. This has several > benefits - you only copy the part of the file system that is in use. > For example, if you have a 40G partition, and only 10G is used, then > you only have to copy 10G, where you have to copy all 30G with dd. > You can also copy to a different size partition. It wil adjust the > file system to the new size. (You must have room for the all the > data on the source partition.) > > The drawback is that it can only copy partitions with a file system > that it understands, and it can have problems with file systems that > have errors on them. > > In any case, when you are coping a disk, unless you are coping to an > identical disk with dd, and coping the entire disk - MBR and all, > you are going to have to re-install grub on the new disk. This is > because of the way the grub first stage works. The first stage only > know how to load the next stage, and it has the physical location of > what it has to load stored as part of the first stage boot loader. > With most coping methods, the second stage is not going to be at > the same place on the disk as it was on the original drive. > > I find that using a tool like the System Rescue CD works well for > this type of job. You boot from it first to copy the disk. Then you > boot from it again after you have the disk in the new system to > re-install grub. You can re-install grub while the disk is still in > the old system, but this is harder for a new user. You can also use > the Fedora install disk in the rescue mode to do the grub re-install. > > http://www.sysresccd.org/ > > Now, if you are using LVM, it gets much harder to do the copy. It > can be done, but as of yet, the tools are for experts. It would be > nice to have a LVM aware version of parted. Have a look at Clonezilla/Clonezilla Live CD www.clonezilla.org It's LVM2 aware but not LVM1 ;-) > Mikkel > -- taharka Lexington, Kentucky U.S.A.
